According to the present invention, in earthmoving operations it is sometimes desirable to increase the traction of rubber-tired work vehicles and/or to increase their resistance to damage due to the environment, such as sharp rocks and the like. To achieve these objectives, flexible belts with track shoes mounted at equally spaced intervals about their outer periphery have been employed over a pneumatic supporting tire carcass. Normally such belts are formed by placing one or more cylindrical reinforcing plies in the central portion of an elastomer cylindrical belt and attaching track shoes thereto by placing a keeper on the inside periphery of the belt for each track shoe on the outer periphery and clamping the belt between the keeper and the underside of its associated track shoe. Reference is made to this assignee's U.S. Pat. No. 3,773,394 issued to Grawey on Nov. 20, 1973 for a more complete description of the flexible track belts described above.
As pointed out in this assignee's U.S. Pat. No. 3,899,220 issued to Grawey et al on Aug. 12, 1975, a particular problem exists relative to the ingress of dirt and other abrasive materials in the area directly under the track shoe, where such materials can cause rapid deterioration of the elastomer portions of the belt and even damage the reinforcing plies, in more severe situations.
This problem occurs because each rectangular shoe's width (as distinguished from its transverse length) is wider than the width of the underlying keeper member associated with it. As a result, the leading and trailing portions of each shoe's undersurface, when the shoe passes into, through and out of the footprint, can separate from the outer circular belt surface, allowing foreign materials to become trapped therebetween. Large sharp rocks are particularly detrimental, as they can penetrate the elastomer surface of the belt to the reinforcing plies, leading to complete belt failure when the reinforcing ply separates.
Normally, the "fit" of the track shoes to the track belt is best in the central or middle portion of the belt where there is the greatest support from the underlying carcass. Thus, the articulation and/or movement of track shoes relative to one another is greatest at the edges of the belt where there is less underlying support. For this reason, the problem is the greatest at the edges and inwardly therefrom for approximately four to six inches.
The sealing ribs between adjacent track shoes disclosed in U.S. Pat. No. 3,899,220 mentioned above, combined with the flat track shoe mounting site vulcanized in the outer cylindrical surface of the belt, are partially effective in reducing this problem, as are the mating ribs and grooves formed with the underside surface of the track shoes and belt surface. However, these features fail to provide increased stiffness in the portions of the belt between adjacent keepers where the flexing of the belt occurs, which leads to the separation of the shoe's surface from the belt surface.